Chattering ISX15

[FrenchFry]

I need to get a real answer from a real pro. I have a 2019 Peterbilt 389 with a 565 ISX15 Cummins. Around 9000 miles I started getting a chatter sound when the engine is under load. It's now at 23200 miles and a little worse. I thought it was a valve train issue. A Peterbilt mechanic thinks it's a gear lash in the front of engine. My fuel mileage has dropped from 5.7-5.8 to 4.2-4.4mpg. Also, I believe coolant is leaking into EGR. I need so.e real answers before this brand new truck ends up as junk.

[Rawze]

If you suspect egr cooler leaking there will usually be signs of it, like IMAP and crossover pipe building up with crud.

Are you doing any oil sampling (with an actual lab, not a speedco quick-check BS machine) to check for higher then normal wear metals or coolant dillusion?
Has the dips$it stealershit even bothered to suggest you do this?

If you want to test egr cooler for leaks ...

Remove the elbow pipe from the back side of it and pressurize the coolant system to 20 psi and let it sit over night. - Check for coolant seepage in the back of egr cooler next day.


As far as fuel mileage loss etc. do the usual tests like pressurize engine and check for CAC, egr and other leaks.

Also ensure your not getting air in the fuel system. could be something as dumb as a fuel filter or line getting air past an o-ring, etc.

Maybe make an appointment with Mr. Hag to have him test drive it and get a second perspective/perhaps different direction to go in.